Limb Girdle Muscular Dystrophy 2B Research Articles

LIMB-GIRDLE MUSCULAR DYSTROPHY I: P.6Functional recovery by readthrough therapy in a knock-in mouse model with nonsense dysferlin mutation

Defects in dysferlin gene cause limb-girdle muscular dystrophy 2B or Miyoshi distal myopathy. Nonsense mutations have been reported to be most common among Korean patients with dysferlinopathy. More than half of the patients have at least one nonsense allele in dysferlin. Readthrough by ataluren is a promising strategy to overcome nonsense mutation, in use for the nonsense-mediated Duchenne muscular dystrophy. We generated a knock-in mouse with p.Q832* mutation, most frequently found among our dysferlinopathy cases. Mice with homozygous p.Q832* mutation lost dysferlin expression at sarcolemma. It performed worse on the Rotarod and forelimb grip test than wild type C57BL6 mice and moved less on activity monitoring. On eccentric contraction ex vivo, extensor digitorum longus muscle from these mice tended to break easily. These abnormalities could successfully be alleviated when the mice were orally administered with ataluren in liquid. Furthermore, ataluren decreased the number of damaged muscle, fiber size variation and serum creatine kinase level. This results support that readthrough strategy with ataluren will also be applicable to patients with nonsense dysferlin mutation.

Exon Skipping in a Dysf-Missense Mutant Mouse Model

Limb girdle muscular dystrophy 2B (LGMD2B) is without treatment and caused by mutations in the dysferlin gene (DYSF). One-third is missense mutations leading to dysferlin aggregation and amyloid formation, in addition to defects in sarcolemmal repair and progressive muscle wasting. Dysferlin-null mouse models do not allow study of the consequences of missense mutations. We generated a new mouse model (MMex38) carrying a missense mutation in exon 38 in analogy to a clinically relevant human DYSF variant (DYSF p.Leu1341Pro). The targeted mutation induces all characteristics of missense mutant dysferlinopathy, including a progressive dystrophic pattern, amyloid formation, and defects in membrane repair. We chose U7 small nuclear RNA (snRNA)-based splice switching to demonstrate a possible exon-skipping strategy in this new animal model. We show that Dysf exons 37 and 38 can successfully be skipped in vivo. Overall, the MMex38 mouse model provides an ideal tool for preclinical development of treatment strategies for dysferlinopathy.

Multiparametric quantitative MRI assessment of thigh muscles in limb-girdle muscular dystrophy 2A and 2B.

The aim of this study was to apply quantitative MRI (qMRI) to assess structural modifications in thigh muscles of subjects with limb girdle muscular dystrophy (LGMD) 2A and 2B with long disease duration. Eleven LGMD2A, 9 LGMD2B patients and 11 healthy controls underwent a multi-parametric 3T MRI examination of the thigh. The protocol included structural T1-weighted images, DIXON sequences for fat fraction calculation, T2 values quantification and diffusion MRI. Region of interest analysis was performed on 4 different compartments (anterior compartment, posterior compartment, gracilis, sartorius). Patients showed high levels of fat infiltration as measured by DIXON sequences. Sartorius and anterior compartment were more infiltrated in LGMD2B than LGMD2A patients. T2 values were mildly reduced in both disorders. Correlations between clinical scores and qMRI were found. qMRI measures may help to quantify muscular degeneration, but careful interpretation is needed when fat infiltration is massive. Muscle Nerve 58: 550-558, 2018.

Analysis of DYSF gene mutations in two pedigrees affected with limb-girdle muscular dystrophy type 2B

To analyze mutations of DYSF gene in two pedigrees affected with limb-girdle muscular dystrophy 2B (LGMD-2B). Genomic DNA was extracted from peripheral blood samples of the two probands and unaffected family members. Variant sites were screened by next-generation sequencing using gene panel as well as Sanger sequencing. Four pathogenic mutations of the DYSF gene were detected, which included a de novo mutation and three mutations with uncertain significance. In pedigree 1, the proband carried compound heterozygous mutations of c.1667T to C (p.Leu556Pro) and c.5567T to A (p.Val1856Glu), which were respectively inherited from her mother and father. Proband of pedigree 2 carried compound heterozygous mutations of c.4853A to G (p.Tyr1618Cys) and c.4876G to A (p.Val1612Ile), among which c.4876G to A (p.Val1626Ile) was also found in his father and grandfather, while c.4853A to G (p.Tyr1618Cys) was detected in his mother and grandmother. The two compound heterozygous mutations of the DYSF gene probably underlie the LGMD2B in the two pedigrees. Next generation sequencing has conferred great advantage for gene diagnosis of hereditary myopathy.

Diltiazem improves contractile properties of skeletal muscle in dysferlin-deficient BLAJ mice, but does not reduce contraction-induced muscle damage.

B6.A‐Dysf prmd/GeneJ (BLAJ) mice model human limb‐girdle muscular dystrophy 2B (LGMD2B), which is linked to mutations in the dysferlin (DYSF) gene. We tested the hypothesis that, the calcium ion (Ca2+) channel blocker diltiazem (DTZ), reduces contraction‐induced skeletal muscle damage, in BLAJ mice. We randomly assigned mice (N = 12; 3–4 month old males) to one of two groups – DTZ (N = 6) or vehicle (VEH, distilled water, N = 6). We conditioned mice with either DTZ or VEH for 1 week, after which, their tibialis anterior (TA) muscles were tested for contractile torque and susceptibility to injury from forced eccentric contractions. We continued dosing with DTZ or VEH for 3 days following eccentric contractions, and then studied torque recovery and muscle damage. We analyzed contractile torque before eccentric contractions, immediately after eccentric contractions, and at 3 days after eccentric contractions; and counted damaged fibers in the injured and uninjured TA muscles. We found that DTZ improved contractile torque before and immediately after forced eccentric contractions, but did not reduce delayed‐onset muscle damage that was observed at 3 days after eccentric contractions.

Elevated TGF β2 serum levels in Emery-Dreifuss Muscular Dystrophy: Implications for myocyte and tenocyte differentiation and fibrogenic processes

ABSTRACTAmong rare diseases caused by mutations in LMNA gene, Emery-Dreifuss Muscular Dystrophy type 2 and Limb-Girdle muscular Dystrophy 1B are characterized by muscle weakness and wasting, joint contractures, cardiomyopathy with conduction system disorders. Circulating biomarkers for these pathologies have not been identified. Here, we analyzed the secretome of a cohort of patients affected by these muscular laminopathies in the attempt to identify a common signature. Multiplex cytokine assay showed that transforming growth factor beta 2 (TGF β2) and interleukin 17 serum levels are consistently elevated in the vast majority of examined patients, while interleukin 6 and basic fibroblast growth factor are altered in subgroups of patients. Levels of TGF β2 are also increased in fibroblast and myoblast cultures established from patient biopsies as well as in serum from mice bearing the H222P Lmna mutation causing Emery-Dreifuss Muscular Dystrophy in humans. Both patient serum and fibroblast conditioned media activated a TGF β2-dependent fibrogenic program in normal human myoblasts and tenocytes and inhibited myoblast differentiation. Consistent with these results, a TGF β2 neutralizing antibody avoided fibrogenic marker activation and myogenesis impairment. Cell intrinsic TGF β2-dependent mechanisms were also determined in laminopathic cells, where TGF β2 activated AKT/mTOR phosphorylation. These data show that TGF β2 contributes to the pathogenesis of Emery-Dreifuss Muscular Dystrophy type 2 and Limb-Girdle muscular Dystrophy 1B and can be considered a potential biomarker of those diseases. Further, the evidence of TGF β2 pathogenetic effects in tenocytes provides the first mechanistic insight into occurrence of joint contractures in muscular laminopathies.

SMAD6 overexpression leads to accelerated myogenic differentiation of LMNA mutated cells

LMNA gene encodes lamins A and C, two major components of the nuclear lamina, a network of intermediate filaments underlying the inner nuclear membrane. Most of LMNA mutations are associated with cardiac and/or skeletal muscles defects. Muscle laminopathies include Emery-Dreifuss Muscular Dystrophy, Limb-Girdle Muscular Dystrophy 1B, LMNA-related Congenital Muscular Dystrophy and Dilated Cardiomyopathy with conduction defects. To identify potential alterations in signaling pathways regulating muscle differentiation in LMNA-mutated myoblasts, we used a previously described model of conditionally immortalized murine myoblasts: H-2K cell lines. Comparing gene expression profiles in wild-type and Lmna∆8–11 H-2K myoblasts, we identified two major alterations in the BMP (Bone Morphogenetic Protein) pathway: Bmp4 downregulation and Smad6 overexpression. We demonstrated that these impairments lead to Lmna∆8–11 myoblasts premature differentiation and can be rescued by downregulating Smad6 expression. Finally, we showed that BMP4 pathway defects are also present in myoblasts from human patients carrying different heterozygous LMNA mutations.

DNA-Mediated Gene Therapy in a Mouse Model of Limb Girdle Muscular Dystrophy 2B

Mutations in the gene for dysferlin cause a degenerative disorder of skeletal muscle known as limb girdle muscular dystrophy 2B. To achieve gene delivery of plasmids encoding dysferlin to hind limb muscles of dysferlin knockout mice, we used a vascular injection method that perfused naked plasmid DNA into all major muscle groups of the hind limb. We monitored delivery by luciferase live imaging and western blot, confirming strong dysferlin expression that persisted over the 3-month time course of the experiment. Co-delivery of the follistatin gene, which may promote muscle growth, was monitored by ELISA. Immunohistochemistry documented the presence of dysferlin in muscle fibers in treated limbs, and PCR confirmed the presence of plasmid DNA. Because dysferlin is involved in repair of the sarcolemmal membrane, dysferlin loss leads to fragile sarcolemmal membranes that can be detected by permeability to Evan’s blue dye. We showed that after gene therapy with a plasmid encoding both dysferlin and follistatin, statistically significant reduction in Evan’s blue dye permeability was present in hamstring muscles. These results suggest that vascular delivery of plasmids carrying these therapeutic genes may lead to simple and effective approaches for improving the clinical condition of limb girdle muscular dystrophy 2B.

P.166 - A knock-in mouse model with nonsense dysferlin mutation

Mutations in the dysferlin gene cause limb-girdle muscular dystrophy 2B or Miyoshi distal myopathy with autosomal recessive inheritance pattern. A few mouse models harboring truncating mutations have been in use for the research of the dysferlinopathy. We found nonsense mutations are most common among Korean patients with dysferlinopathy; more than half of the patients have at least one nonsense allele, which could be mitigated by readthrough strategy. Thus we generated a knock-in mouse with p.Q832* mutation, most frequently found among our dysferlinopathy cases. Mice with homozygous p.Q832* mutation, named dqx, performed poorer on Rotarod and treadmill test than wild type C57BL6 mice and moved less on activity monitoring. On eccentric contraction ex vivo, extensor digitorum longus muscle from dqx tended to break easily on the first few contractions. All these abnormality could successfully be alleviated when the mice were administered with gentamicin for 3 weeks. These results support that readthrough strategy may also be applicable to nonsense dysferlinopathy patients.

Intermittent Glucocorticoid Dosing Improves Muscle Repair and Function in Mice with Limb-Girdle Muscular Dystrophy

The muscular dystrophies are genetically diverse. Shared pathological features among muscular dystrophies include breakdown, or loss of muscle, and accompanying fibrotic replacement. Novel strategies are needed to enhance muscle repair and function and to slow this pathological remodeling. Glucocorticoid steroids, like prednisone, are known to delay loss of ambulation in patients with Duchenne muscular dystrophy but are accompanied by prominent adverse effects. However, less is known about the effects of steroid administration in other types of muscular dystrophies, including limb-girdle muscular dystrophies (LGMDs). LGMD 2B is caused by loss of dysferlin, a membrane repair protein, and LGMD 2C is caused by loss of the dystrophin-associated protein, γ-sarcoglycan. Herein, we assessed the efficacy of steroid dosing on sarcolemmal repair, muscle function, histopathology, and the regenerative capacity of primary muscle cells. We found that in murine models of LGMD 2B and 2C, daily prednisone dosing reduced muscle damage and fibroinflammatory infiltration. However, daily prednisone dosing also correlated with increased muscle adipogenesis and atrophic remodeling. Conversely, intermittent dosing of prednisone, provided once weekly, enhanced muscle repair and did not induce atrophy or adipogenesis, and was associated with improved muscle function. These data indicate that dosing frequency of glucocorticoid steroids affects muscle remodeling in non-Duchenne muscular dystrophies, suggesting a positive outcome associated with intermittent steroid dosing in LGMD 2B and 2C muscle.

Treatment with Recombinant Human MG53 Protein Increases Membrane Integrity in a Mouse Model of Limb Girdle Muscular Dystrophy 2B

Limb girdle muscular dystrophy type 2B (LGMD2B) and other dysferlinopathies are degenerative muscle diseases that result from mutations in the dysferlin gene and have limited treatment options. The dysferlin protein has been linked to multiple cellular functions including a Ca2+-dependent membrane repair process that reseals disruptions in the sarcolemmal membrane. Recombinant human MG53 protein (rhMG53) can increase the membrane repair process in multiple cell types both invitro and invivo. Here, we tested whether rhMG53 protein can improve membrane repair in a dysferlin-deficient mouse model of LGMD2B (B6.129-Dysftm1Kcam/J). We found that rhMG53 can increase the integrity of the sarcolemmal membrane of isolated muscle fibers and whole muscles in a Ca2+-independent fashion when assayed by a multi-photon laser wounding assay. Intraperitoneal injection of rhMG53 into mice before acute eccentric treadmill exercise can decrease the release of intracellular enzymes from skeletal muscle and decrease the entry of immunoglobulin G and Evans blue dye into muscle fibers invivo. These results indicate that short-term rhMG53 treatment can ameliorate one of the underlying defects in dysferlin-deficient muscle by increasing sarcolemmal membrane integrity. We also provide evidence that rhMG53 protein increases membrane integrity independently of the canonical dysferlin-mediated, Ca2+-dependent pathway known to be important for sarcolemmal membrane repair.

Coupling of excitation to Ca2+ release is modulated by dysferlin.

Dysferlin, the protein missing in limb girdle muscular dystrophy 2B and Miyoshi myopathy, concentrates in transverse tubules of skeletal muscle, where it stabilizes voltage-induced Ca2+ transients against loss after osmotic shock injury (OSI). Local expression of dysferlin in dysferlin-null myofibres increases transient amplitude to control levels and protects them from loss after OSI. Inhibitors of ryanodine receptors (RyR1) and L-type Ca2+ channels protect voltage-induced Ca2+ transients from loss; thus both proteins play a role in injury in dysferlin's absence. Effects of Ca2+ -free medium and S107, which inhibits SR Ca2+ leak, suggest the SR as the primary source of Ca2+ responsible for the loss of the Ca2+ transient upon injury. Ca2+ waves were induced by OSI and suppressed by exogenous dysferlin. We conclude that dysferlin prevents injury-induced SR Ca2+ leak. Dysferlin concentrates in the transverse tubules of skeletal muscle and stabilizes Ca2+ transients when muscle fibres are subjected to osmotic shock injury (OSI). We show here that voltage-induced Ca2+ transients elicited in dysferlin-null A/J myofibres were smaller than control A/WySnJ fibres. Regional expression of Venus-dysferlin chimeras in A/J fibres restored the full amplitude of the Ca2+ transients and protected against OSI. We also show that drugs that target ryanodine receptors (RyR1: dantrolene, tetracaine, S107) and L-type Ca2+ channels (LTCCs: nifedipine, verapamil, diltiazem) prevented the decrease in Ca2+ transients in A/J fibres following OSI. Diltiazem specifically increased transients by ∼20% in uninjured A/J fibres, restoring them to control values. The fact that both RyR1s and LTCCs were involved in OSI-induced damage suggests that damage is mediated by increased Ca2+ leak from the sarcoplasmic reticulum (SR) through the RyR1. Congruent with this, injured A/J fibres produced Ca2+ sparks and Ca2+ waves. S107 (a stabilizer of RyR1-FK506 binding protein coupling that reduces Ca2+ leak) or local expression of Venus-dysferlin prevented OSI-induced Ca2+ waves. Our data suggest that dysferlin modulates SR Ca2+ release in skeletal muscle, and that in its absence OSI causes increased RyR1-mediated Ca2+ leak from the SR into the cytoplasm.

A novel de nova missense LMNA mutation in a Turkish patient with laminopathies

The laminopathies associated to the lamin A/C (LMNA) gene mutations at chromosome 1q22 region; comprise different well-characterized phenotypes. Some of the multi-systemic laminopathies are lipodystrophy, Charcot-Marie Tooth disease (CMT), Emery-Dreifuss muscular dystrophy (EDMD) and Limb Girdle muscular dystrophy 1B (LGMD1B). The LGMD1B is characterized by a symmetric proximal weakness starting from the legs, atrioventricular conduction disturbances and dysrhythmias. 17-year-old female patient had suffered from progressive muscle weakness. Patient's testing of deep-tendon reflexes were negative in neurological examination. She had positive Gower's sign and proximal muscle strength was reduced with score of 4/5. She had foot-drop gait and atrophy of lower extremities. Her feet showed a mild pescavus deformity and could not lift up by herself. Serum creatine kinase level was normal. Followed by pediatric cardiology due to first degree A–V block. Cardiac echocardiogram demonstration was normal. Nerve conduction velocity was within normal limits and electromyogram was indicative of myopathy. Muscular histology was compatible with muscular dystrophy and showed a nonspecific excess of lipid droplets. With the diagnosis of Limb Girdle muscular dystrophy 1B; LMNA gene sequence analysis including all coding exons and exon-intron boundaries was done and LMNA NM_170707.3:c.734T>C; (p.Leu245Pro) heterozygous missense mutation was detected. This mutation was first reported by from Turkish population. In silico analysis with Mutation Taster, Polyphen2, SIFT was predict this variant as a disease causing mutation. In order to show familial segregation, mother and father also were included in the study. Her parents were no carriers of the mutation. This case illustrate the necessity of correct diagnosis, evaluation, and follow up of cardiac problems due to the wide clinical spectrum and high prevalence of cardiac conduction block in patients with LGMD1B.

Abnormal lipid metabolism in skeletal muscle tissue of patients with muscular dystrophy: In vitro, high-resolution NMR spectroscopy based observation in early phase of the disease

PurposeQualitative (assignment of lipid components) and quantitative (quantification of lipid components) analysis of lipid components were performed in skeletal muscle tissue of patients with muscular dystrophy in early phase of the disease as compared to control/normal subjects. MethodsProton nuclear magnetic resonance (NMR) spectroscopy based experiment was performed on the lipid extract of skeletal muscle tissue of patients with muscular dystrophy in early phase of the disease and normal individuals for the analysis of lipid components [triglycerides, phospholipids, total cholesterol and unsaturated fatty acids (arachidonic, linolenic and linoleic acid)]. Specimens of muscle tissue were obtained from patients with Duchenne muscular dystrophy (DMD) [n=11; Age, Mean±SD; 9.2±1.4years; all were males], Becker muscular dystrophy (BMD) [n=12; Age, Mean±SD; 21.4±5.0years; all were males], facioscapulohumeral muscular dystrophy (FSHD) [n=11; Age, Mean±SD; 23.7±7.5years; all were males] and limb girdle muscular dystrophy-2B (LGMD-2B) [n=18; Age, Mean±SD; 24.2±4.1years; all were males]. Muscle specimens were also obtained from [n=30; Mean age±SD 23.1±6.0years; all were males] normal/control subjects. ResultsAssigned lipid components in skeletal muscle tissue were triglycerides (TG), phospholipids (PL), total cholesterol (CHOL) and unsaturated fatty acids (arachidonic, linolenic and linoleic acid)]. Quantity of lipid components was observed in skeletal muscle tissue of DMD, BMD, FSHD and LGMD-2B patients as compared to control/normal subjects. TG was significantly elevated in muscle tissue of DMD, BMD and LGMD-2B patients. Increase level of CHOL was found only in muscle of DMD patients. Level of PL was found insignificant for DMD, BMD and LGMD-2B patients. Quantity of TG, PL and CHOL was unaltered in the muscle of patients with FSHD as compared to control/normal subjects. Linoleic acids were significantly reduced in muscle tissue of DMD, BMD, FSHD and LGMD-2B as compared to normal/control individuals. ConclusionsResults clearly indicate alteration of lipid metabolism in patients with muscular dystrophy in early phase of the disease. Moreover, further evaluation is required to understand whether these changes are primary or secondary to muscular dystrophy. In future, these findings may prove an additional and improved approach for the diagnosis of different forms of muscular dystrophy.

Dysferlin-mediated phosphatidylserine sorting engages macrophages in sarcolemma repair.

Failure to repair the sarcolemma leads to muscle cell death, depletion of stem cells and myopathy. Hence, membrane lesions are instantly sealed by a repair patch consisting of lipids and proteins. It has remained elusive how this patch is removed to restore cell membrane integrity. Here we examine sarcolemmal repair in live zebrafish embryos by real-time imaging. Macrophages remove the patch. Phosphatidylserine (PS), an ‘eat-me' signal for macrophages, is rapidly sorted from adjacent sarcolemma to the repair patch in a Dysferlin (Dysf) dependent process in zebrafish and human cells. A previously unrecognized arginine-rich motif in Dysf is crucial for PS accumulation. It carries mutations in patients presenting with limb-girdle muscular dystrophy 2B. This underscores the relevance of this sequence and uncovers a novel pathophysiological mechanism underlying this class of myopathies. Our data show that membrane repair is a multi-tiered process involving immediate, cell-intrinsic mechanisms as well as myofiber/macrophage interactions.

P.39 - Quantitative assessment of muscle involvement in limb girdle muscular dystrophy 2B

P.39 - Quantitative assessment of muscle involvement in limb girdle muscular dystrophy 2B

Dysferlin Binds SNAREs (Soluble N-Ethylmaleimide-sensitive Factor (NSF) Attachment Protein Receptors) and Stimulates Membrane Fusion in a Calcium-sensitive Manner

Resealing of tears in the sarcolemma of myofibers is a necessary step in the repair of muscle tissue. Recent work suggests a critical role for dysferlin in the membrane repair process and that mutations in dysferlin are responsible for limb girdle muscular dystrophy 2B and Miyoshi myopathy. Beyond membrane repair, dysferlin has been linked to SNARE-mediated exocytotic events including cytokine release and acid sphingomyelinase secretion. However, it is unclear whether dysferlin regulates SNARE-mediated membrane fusion. In this study we demonstrate a direct interaction between dysferlin and the SNARE proteins syntaxin 4 and SNAP-23. In addition, analysis of FRET and in vitro reconstituted lipid mixing assays indicate that dysferlin accelerates syntaxin 4/SNAP-23 heterodimer formation and SNARE-mediated lipid mixing in a calcium-sensitive manner. These results support a function for dysferlin as a calcium-sensing SNARE effector for membrane fusion events.

Limb-Girdle Muscular Dystrophy 2B and Miyoshi Presentations of Dysferlinopathy

We report the following 2 subtypes of progressive limb-girdle dystrophy type 2B: limb-girdle muscular dystrophy type 2B (LGMD2B) and Miyoshi. The first patient described had weakness in the anterior thigh muscles (LGMD2B) and the second patient had calf muscle weakness and atrophy (Miyoshi). Literature review was performed and LGMD2B was compared and distinguished from other myopathies of similar nature. Genetic testing with polymerase chain reaction analysis of the DYSF gene confirmed the diagnosis in both patients. Additional findings of histopathology, specific stain for sarcolemmal membrane protein, Western blot analysis and clinical presentation clinched the diagnosis further of dysferlinopathy (LGMD2B) in both our patients. Currently, there is no definitive treatment on the horizon and immunosuppressive therapy is not recommended for this condition. Gene therapy may have a future role, but at present, muscle-strengthening exercises and patient awareness are the mainstays.

Advances in muscle imaging for Emery-Dreifuss muscular dystrophy

Laminopathies are a heterogeneous group of disorders related to alterations on genes coding for proteins of the nuclear envelope. Among these clinical entities, there are several diseases affecting mainly the cardiac and skeletal muscles. These disorders include forms with a selective cardiac compromise and muscular dystrophies (autosomal and X-linked forms of Emery-Dreifuss muscular dystrophy, Limb girdle muscular dystrophy 1B, LMNA-related congenital muscular dystrophy and other rare clinical entities). We performed imaging studies on a large cohort of subjects bearing either LMNA or EMD gene mutations; each patient enrolled displayed variable compromise on posterior legs’ muscles, ranging from mild compromise on soleus and medial head of gastrocnemius to overt alterations on soleus, medial head of gastrocnemius [1,3]. Of note, we saw that even subjects presenting with clinically selective cardiac compromise displayed, on imaging studies, variable alterations on skeletal muscles. This findings showed a continuum in skeletal muscles compromise among different phenotypes related to LMNA or EMD gene mutations and lead to hypothesize a common mechanism in the process of damage of skeletal muscles fibers.

Dysferlinopathy in Iran: Clinical and genetic report

BackgroundDysferlinopathy is caused by a very wide range of autosomal recessively inherited mutations of the Dysferlin gene. It causes a spectrum of muscle diseases including limb-girdle muscular dystrophy (LGMD) 2B and Miyoshi myopathy (MM). We describe the clinical course and mutational analyses of 15 Iranian patients with dysferlinopathy from 9 different families. MethodsGenomic DNA was extracted from peripheral blood and 55 exons and flanking intronic boundaries of the dysferlin gene (DYSF; NM_003494.2) were screened for mutations and analyzed. ResultsFrom 15 studied patients in 9 families, 5 patients were male. Seven families had consanguineous marriage. Median age of onset was 16.8; and the median age of diagnosis was 26.6. The onset was clearly distal in 7 patients, and proximal in 6 patients. Three patients had partial biceps atrophy and 13 showed prominent calf muscle wasting. Foot plantar flexors, deep finger flexors and hip adductors were predominantly involved. Genetic testing showed homozygous mutation of dysferlin gene in 9 probands, 5 of which were not previously reported. ConclusionThis work, in fact, may help shed some light on the pattern of this morbidity in Iran, an effort that may have not been attempted so far.